Acer Aspire S3-391 - Manual (Page 79)

78 - Acer Theft Shield
Note: If your phone does not have a barcode reader installed, you will
need to download one before you can scan the QR code.
Once you have downloaded the Android app to your phone, click Next to
start setting up Acer Theft Shield. Click Start to turn on your notebook’s
Wi-Fi hotspot feature, this will allow your phone to detect the notebook.
Using Acer Theft Shield
General
Once you have selected the method to use, you will be shown the General
page which allows you to activate Acer Theft Shield and select a hotkey
combination to activate Acer Theft Shield.
You can press the hotkey combination to protect your computer at any
time.